HP4a_9_Krummrich_rev0605

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Fuel Cell Methanol Reformer System for Submarines

S. Krummrich

This document appeared in

Detlef Stolten, Thomas Grube (Eds.):

18th World Hydrogen Energy Conference 2010 - WHEC 2010

Parallel Sessions Book 3: Hydrogen Production Technologies - Part 2

Proceedings of the WHEC, May 16.-21. 2010, Essen

Schriften des Forschungszentrums Jlich / Energy & Environment, Vol. 78-3

Institute of Energy Research - Fuel Cells (IEF-3)

Forschungszentrum Jlich GmbH, Zentralbibliothek, Verlag, 2010

ISBN: 978-3-89336-653-8


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Fuel Cell Methanol Reformer System for Submarines

Stefan Krummrich, Howaldtswerke-Deutsche Werft GmbH, Germany

1 Introduction

After the successful market introduction of Fuel Cell powered submarines, HDW is ahead of

the market in the field of conventional submarines equipped with Air-Independent propulsion

(AIP) systems. Today HDW offers different types of submarines including fuel cell systems

like the classes U212A (Germany, Italy) or the class 214. All these submarines are based on

fuel cell systems with metal hydride storage cylinders for the hydrogen.

In the recent decades conventional submarines were based on diesel-electric propulsion with

lead batteries for submerged operation. Improvements to these systems have been gradually

since WW II, small steps leading to improvements mainly in the field of signatures of thesubmarine. But still the snorkel operation to recharge the batteries is mandatory at least

every few days.

In Comparison submarines equipped with Fuel Cells offer remarkable operational

advantages. The AIP-equipped submarines can stay submerged during operation for a much

longer time than before at similar performance regarding noise level. This is caused by the

fact that fuel cells produce electrical energy without any moving parts, similar to a battery.

Generally the requirements of the AIP Systems in addition to the enlarged submerged

operation period are as follows:

high efficiency (low heat discharge to sea water)

low noise level

low magnetic signature

small size

low weight

low effort for maintenance / no extra crew

Fuel cells have been under development by Howaldtswerke-Deutsche Werft for more than

20 years. In 1988 first sea tests were performed with a fuel cell plant in the submarine U1.

Today four submarines of Class U212A are in service at the German Navy. Furthermore

several export contracts could be realised, also with some submarines already in operation.

Compared to other applications, fuel cells in submarines made its way because of theenormous customer benefit they offer. The development was based on a completely new

approach, not on the replacement of any existing system [1].

Proceedings WHEC2010 213


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2 Proven Technology

The system installed onboard the HDW submarines today consists of the components shown

in Figure 1.

Figure 1: Overview about Fuel Cell System components.

The PEM fuel cells deliver the electrical energy for the boats power network system via a

DC/DC-converter. The waste heat from the fuel cell is used to release the hydrogen from the

metal hydride storage cylinders and to evaporate liquid oxygen for the operation of the H2/O2

fuel cells. The reaction water is collected onboard to prevent the need for weight

compensation with sea water. In case of Class 209 and 214, two Siemens FCM 120 Fuel

Cells are used, with 240 kW maximum system power output [2].

In total the system has a very high electrical efficiency of up to 60 %, and offers many

benefits regarding submarine specific requirements.

3 Reasons for Reforming onboard Submarines

Even if the existing fuel cell system offers many advantages, the tendency in submarine

development goes to higher amounts of stored AIP-Energy. The system based on metal

hydride storage is relatively heavy, resulting in the fact that the amount of hydrogen stored

onboard is limited by the size of the submarine, having in mind the principle of Archimedes.

Generally liquid fuels have high volumetric and gravimetric energy content and are easy to

handle. These advantages in combination with the fuel cells performance motivated HDW to

start with the development of a reformer system for onboard hydrogen production [3].

214 Proceedings WHEC2010


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4 Choice of Feedstock

The choice of the best fuel for a reformer system for submarines has great influence not only

on the system design, but also on the submarines design and performance. Generally the

feedstock for a reformer system can be hydrocarbon or alcohol. Compared to the storage of

pure hydrogen, this implies the production of CO2 onboard. As CO2 cannot be stored

onboard like e.g. the product water of the fuel cell, it has to be discharged into the

surrounding sea. To realize a weight balanced system (principle of Archimedes), the lost

weight of the CO2 has to be compensated with sea water.

The reformer has to be operated with fuel + oxygen (+ water). The oxygen is stored onboard

as a liquid in a cryogenic tank. This LOX-tank is the dominant component regarding system

size. Consequently, the oxygen consumption of the AIP-System is very important and should

be kept as low as possible. Considering the entire AIP-System, the chemical products are

water (H2O) and carbon dioxide (CO2). Therefore, the ratio of H to C in the chemical structure

should be high, because the oxidation of C requires more oxygen then the oxidation of H.Furthermore the overall system efficiency is of importance for the oxygen consumption, and

of course for the fuel consumption.

Further factors are important for the choice of feedstock are the worldwide availability, the

safety (handling etc.), the purity (avoidance of additional adsorbers etc.) and the reforming

temperature to keep the reformer easy.

Summarized the requirements for the feedstock are:

high hydrogen content in the chemical structure

high efficiency of the reforming process

worldwide availability

easy storage onboard

easy handling for e.g. refuelling

easy reformation

HDW has considered three feedstocks for submarine reforming: Diesel (C13.57H27.14) Ethanol

(C2H5OH) and Methanol (CH3OH). The final choice was made for Methanol because of the

following reasons4:

H/C ratio is highest for Methanol

highest efficiency of reforming process

very easy reformation (T app. 250 C; for Diesel > 850 C, for Ethanol >700 C

required)

worldwide availability

high purity (no sulphur etc.)

5 System Configuration

At the beginning of the development the requirements for the reformers have been defined. A

major requirement was the operation based on the existing and proven Siemens Fuel Cells.

Furthermore the exhaust gas (CO2) pressure should be high, to enable the discharge of

exhaust gas into the surrounding seawater without the need for an additional exhaust gas



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compressor. Of major importance was the overall system efficiency and the reliability and

availability of the system.

Based on these requirements, the choice was a methanol steam reformer system operated

at elevated pressure. The hydrogen purification is performed with a membrane purification

unit. The required thermal energy is produced in a high-pressure oxygen burner. An overview

about the process is shown in Figure 2.

Figure 2: Overview of Methanol Reformer System.

The methanol is mixed with water, evaporated and fed to the steam reformer. The reforming

reactor is heated by a boiling water cycle. The methanol-water mixture is converted into a

hydrogen-rich gas mixture at typical methanol reforming temperatures. This reformate gas is

further processed in a gas purification unit. The major fraction of hydrogen is separated and

can be fed directly to the Siemens Fuel Cell. The rest of the reformate gas is burned, to

provide the required heat for the reforming process. The only product gas from the reformer

is CO2 at elevated pressure, the H2O in the exhaust gas is condensed and reused internally.

The methanol reformer itself will be operated in an encapsulation comprising several safety

features, to prevent the crew from any harmful gases and liquids.

6 Status of Development

The reformer development at HDW started many years ago under the assumption that the

German Navy would choose reformer technology for their second batch of Class 212

Submarines. After the decision to stay with the metal hydride storage cylinders, the

development of reformer systems for submarines has been performed with reduced

resources. Today the efforts have been increased again, to have the chance to offer the

system to potential costumers worldwide.

HDW operates a full size functional demonstrator in the test facilities in Kiel. The

demonstrator has formerly been built up with COTS components most of the components

used cannot be applied onboard a submarine. Now single components and systems are



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developed and installed to achieve a submarine-proven design, and to test them under real

process conditions in the functional demonstrator.

The major milestone in 2009 was the realisation and testing of a new gas purification. The

purification unit has passed a shock test under operating conditions (temperature, and

pressure difference) as part of military approval of the component. Furthermore the

performance of the unit could be verified. The hydrogen is of a very high purity, the

requirement of the Siemens Fuel Cell is fulfilled. In February 2010 the Reformer has been

coupled with a submarine fuel cell with very good results no difference in fuel cell

performance could be detected compared to Hydrogen from the cryogenic storage tank at

HDW.

The test runs with the reformer showed a very high efficiency of the system. The efficiency

(Hu_H2 / Hu_CH3OH) was measured to be >90 %.

The system integration has been worked out, a picture of the unit is shown in Figure 3.

Another picture including the encapsulation is shown in Figure 4.

Figure 3: Methanol Reformer System

Figure 4: Encapsulation of MRS



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7 Outlook

The reformer system will be further developed to meet all demands for onboard operation.

During a reconstruction period in this year the heat integration will be further improved, and

the valves in the plant will be replaced.

The operation of Reformer with fuel cell will be extended to implement and test a new

DC/DC-converter.

Further major steps in the development will be the operation of the reformer system together

with an exhaust gas treatment unit, to discharge CO2 directly into the surrounding seawater.

All these further steps will bring the Fuel Cell Methanol Reformer System closer to

application. With this technology HDW offers a second option of Fuel Cell AIP solution, that

will confirm the leadership of HDW in AIP-Systems for submarines.

References

[1] Pommer, H.; Hauschildt, P.; Teppner, R. and Hartung, W. (2006) - Air Independent

Propulsion System for Submarines. ThyssenKrupp techforum 01/2006

[2] Hammerschmidt, A. (2006) - Fuel Cell Propulsion of Submarines.Advanced Naval

Propulsion Symposium 2006

[3] Psoma, A.; Sattler, G. (2002) - Fuel cell systems for submarines: from the first idea to

serial production. Journal of Power Sources, Volume 106

[4] Kolb, G. (2008) Fuel Processing for Fuel Cells. Wiley-VCH


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